Polymer powders for SIB processes

ABSTRACT

A process of selective inhibition of bonding (SIB) to produce three-dimensional objects is used to obtain high-quality moldings. High-quality moldings can be produced by using pulverulent materials which have a median particle size of from 10 to 200 μm in which at least one polymer or copolymer selected from polyester, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate (PMMA), PMMI, ionomer, polyamides, copolyester, copolyamides, terpolymers, or ABS, or a mixture of these, is present.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a polymer powder which can be used forproducing three-dimensional objects by means of selective inhibition ofbonding (SIB), and to a process in which these powders are used.

2. Description of the Related Art

Very recently a need for the rapid production of prototypes has arisen.Selective laser sintering (SLS) is a process particularly well suited torapid prototyping. In the SLS process, polymer powders are selectivelyand briefly irradiated in a chamber with a laser beam. Particles ofpowder exposed to the laser beam melt. The molten particles fuse andsolidify to give a solid mass. Three-dimensional bodies can be producedsimply and rapidly by repeatedly applying fresh layers of polymer powderand exposing the fresh layers of polymer powder to the laser beam.

The process of laser sintering (rapid prototyping) to produce moldingsfrom pulverulent polymers is described in detail in U.S. Pat. No.6,136,948 and WO 96/06881. A wide variety of polymers and copolymers aredisclosed to be useful in this application, including for examplepolyacetate, polypropylene, polyethylene, ionomers, and nylon-11.

Nylon-12 (PA 12) powder has proven particularly successful for producingengineering components by industrial laser sintering. Parts manufacturedfrom PA12 powder meet high mechanical requirements and have propertiesnearly the same as those of parts produced by mass-production techniquessuch as injection molding or extrusion.

A material particularly well suited is nylon-12 with a melting point offrom 185 to 189° C., an enthalpy of fusion of 112±17 J/g, and asolidification point of from 138 to 143° C., as described in EP 0 911142 (incorporated herein by reference). It is preferable to use powderswhose median particle size is from 50 to 150 μm, for example thoseobtained as in DE 197 08 946 or else DE 44 21 454 (each of which isincorporated herein by reference).

The SLS process however suffers from high equipment costs, in particularthe cost of the laser. Further, the processing speed in laser sinteringis relatively slow because large areas have to be scanned by a pointlight source. These disadvantages have inhibited wide adoption of thisprocess for producing computer-designed objects, and therefore theapplication of the SLS process currently remains restricted to rapidprototyping. An additional problem with SLS is the process' inability toprocess colored powders, especially dark-colored powders.

Processes which are capable of use in both rapid prototyping and formanufacturing common household goods have to be significantly simpler tocarry out in comparison to SLS, and should in particular be capable ofoperating without the expensive and complicated apparatus and startingmaterials required in the conventional process.

Koshnevis (WO 01/38061) has developed a process in which a mass is builtup of layers of a powder to be bonded (sintered). After the applicationof each powder layer, selected regions of the layer are treated with abonding inhibitor so that bonding takes place only in the regions of thecross section of the three-dimensional article. Bonding (sintering) maytake place after each treatment of a layer with a bonding inhibitor.However, it is also possible to sinter the mass, e.g. in an oven, afterall of the layers have been completed. Since the regions which arebonded are only those which have not come into contact with the bondinginhibitor, the result is a three-dimensional body having a layeredstructure.

WO 01/38061 mentions polymer powders and metal powders generally asmatrix materials. The disadvantage with most polymer powders isrelatively high shrinkage, arising in particular during the sintering ofpolymer powders. The processing temperatures of some polymer powders aremoreover unsuitable in sintering because the high temperatures requiredduring processing can cause technical problems during processing.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide polymerpowders which are particularly well suited for use as a matrix materialin the process described in WO 01/38061, for producing three-dimensionalobjects by means of selective inhibition of bonding.

Surprisingly, it has been found that powders in which polymers orcopolymers selected from polyester, polyvinyl chloride, polyacetal,polypropylene, polyethylene, polystyrene, polycarbonate, PMMA, PMMI,ionomer, polyamides, copolyester, copolyamides, terpolymers, oracrylonitrile-butadiene-styrene copolymers (ABS), or a mixture of these,is present, and which have a median particle size of from 10 to 200 μm,are particularly well suited for producing three-dimensional objects bymeans of selective inhibition of bonding, in particular in processes inwhich the bonding takes place via radiated heat (sinter processes).

DETAILED DESCRIPTION OF THE INVENTION

The present invention therefore provides a process for producing athree-dimensional object, which includes:

a) providing a layer of pulverulent material,

b) applying, bonding inhibitors to selected regions of the layer froma), the manner of selection of the regions on which the bondinginhibitor is placed being in accordance with the cross section of thethree-dimensional object, and specifically being such that bondinginhibitors are applied only to the regions which are not part of thecross section of the three-dimensional object,

c) repeating steps a) and b) until all of the cross-sectional areas ofwhich the three-dimensional object is composed form a matrix, and theouter boundaries of the object are formed by the interface betweenpulverulent material with applied bonding inhibitor and untreatedpulverulent material, and

d) treating the layers at least once so that bonding takes place betweenpulverulent material not provided with a bonding inhibitor,

wherein the pulverulent material has a median particle size of from 10to 200 μm and is at least one polymer or copolymer selected frompolyester, polyvinyl chloride, polyacetal, polypropylene, polyethylene,polystyrene, polycarbonate, polymethyl methacrylate (PMMA),poly(N-methylmethacrylimide) (PMMI), ionomer, polyamides, copolyester,copolyamides, terpolymers, or acrylonitrile-butadiene-styrenecopolymers, or a mixture of these.

The present invention also provides a molding produced by the process ofthe invention, and pulverulent material which is suitable for use in aprocess of the invention. Moldings may be sintered shaped bodies.

By using pulverulent material which has a median particle size of from10 to 200 μm, and in which at least one polymer or copolymer selectedfrom polyacetal, polyvinyl chloride, polypropylene, polyethylene,polystyrene, polycarbonate, PMMA, PMMI, ionomer, polyamides, or amixture of these, is present, components thus produced have theadvantage of exhibiting significantly less shrinkage than componentscomposed of polymer materials which do not meet the abovementionedrequirements. The use of pulverulent material within the statedboundaries permits adjustment of the roughness of the surfaces of themoldings produced therefrom.

The use of amorphous or semicrystalline polymers or copolymers whosemelting point is above 85° C. and below 200° C. can substantiallyeliminate any high degree of shrinkage. Furthermore, the use ofpulverulent materials where the melting point of the polymers orcopolymers is between 85 and 200° C. can make it unnecessary to use anapparatus of complicated design and expensive materials for constructingthe apparatus, in particular in relation to thermal insulation orthermal conductivity.

Depending on the inhibitor system used in the process, there may be apreference for some polymers or polymer mixtures. The use of pulverulentmaterial with the specified parameters in the SIB process ensuresproblem-free treatment of the material with inhibitor without any riskthat the inhibitor will wet the pulverulent material outside the desiredregion, as can, for example, be the case if the bulk density of thepulverulent material is too low.

The present process is unlike the known laser-sintering (SLS) process,insofar as the present process permits production of prototypes or shortproduction runs from materials that comprise colored pigments therebyallowing the mass produced resin to be produced on a small scale orprototype scale. In contrast, when an SLS process is used, the use ofdark-pigmented material is impossible due to the use of a laser.

The process of the invention is described below by way of examples, thatare not intended to limit the invention.

The process of the invention for producing a three-dimensional object,includes

a) providing or applying a layer of pulverulent material,

b) applying one or more bonding inhibitors to one or more selectedregions of the layer from a), the manner in which the bonding inhibitoris placed on the layers corresponding to the cross section of thethree-dimensional object to be produced, application is specificallysuch that bonding inhibitors are applied only to the regions which arenot part of the cross section of the three-dimensional object,

c) repeating steps a) and b) until all of the cross-sectional areas forma matrix, and the outer boundaries of the object are formed by theinterface between pulverulent material with applied bonding inhibitorand untreated pulverulent material, and

d) treating the layers at least once so that bonding takes place betweenpulverulent material to which no bonding inhibitor has been applied,

wherein the pulverulent material has a median particle size of from 10to 200 μm and contains at least one polymer or copolymer selected frompolyester, polyvinyl chloride, polyacetal, polypropylene, polyethylene,polystyrene, polycarbonate, PMMA, PMMI, ionomer, polyamides,copolyester, copolyamides, terpolymers, or ABS, or a mixture of these.The pulverulent material may contain only the copolymer or polymer, ormay contain additional materials. The process of the invention is basedon the process described in WO 01/38061 (expressly incorporated hereinby reference). WO 01/38061 provides a detailed description of thefunctional principle of the SIB process.

A consequence of the application of the bonding inhibitor in step b),which is usually computer-controlled, using CAD applications tocalculate the cross-sectional areas, is that only untreated powderparticles are bonded in a subsequent treatment step. The inhibitor istherefore only applied to selected regions of the layer from a) wherethese regions are not part of the cross section of the three-dimensionalobject to be provided, but rather surround the cross-sectional areas.One example of a method of applying the pulverulent material is with useof a printing head provided with nozzles. After the final treatment stepd), the process of the invention gives a matrix with, in part, bondedpulverulent material, revealing the solid three-dimensional object afterremoval of the non-bonded powder.

The pulverulent layer may be provided by physical or chemical processes.Physical processes include pouring and/or forming and chemical processesinclude such processes as chemical vapor deposition.

Depending on the manner in which the process of the invention is carriedout, treatment may be carried out after each or repeated steps b),and/or after step c). The sequence in relation to the treatment in stepd), i.e. the bonding of the pulverulent material, depends on thephysical or chemical process used to bond at least some of thepulverulent material. If the treatment in step d) is intended to takeplace after step c), it has to be ensured that reaction can take placebetween the pulverulent material not treated with bonding inhibitor inall of the layers. When the process is carried out in this way, thepreferred method of bonding the pulverulent material uses heat, achemical reaction, or a thermally initiated chemical reaction. The useof photons, e.g. UV radiation for crosslinking of pulverulent particles,takes place preferably in those embodiments of the process of theinvention in which step d) takes place after every step b).

Available physical processes are any of the processes which permitsimultaneous or near-simultaneous bonding of pulverulent material in oneor more layers, with the exception of the pulverulent material to whichan inhibitor has been applied. Particularly preferred physical processesare those processes in which at least a part of the pulverulent materialis sintered or melted. Preferred processes utilize an increase in thetemperature which may be achieved by irradiation, in particular usingphotons, radiated heat, or microwave radiation, by increasing theambient temperature, by increasing the pressure, and/or by chemicalreaction.

Available chemical processes are likewise various chemical reactionprocesses which permit bonding of at least a part of the pulverulentmaterials to which an inhibitor has not been applied. These reactionprocesses may in particular lead to the formation of covalent or ionicbonds between molecules or elements of one or more powder particles withmolecules or elements of one or more adjacent powder particles. Examplesof suitable reactions are any of the well-known crosslinking reactionsor polymerization reactions. Examples of these reactions includefree-radical or ionic polymerization, esterification reactions,polyaddition, or polycondensation.

Treating the pulverulent material to cause bonding may also include acombination of chemical and physical processes. For example, thepulverulent material may, at least in part, have reactive groups at thesurface which react with one another on heating. When such groups arepresent, a material which inactivates the reactive groups even withoutheating may be used as an inhibitor.

Bonding inhibitors include, inter alia, those described in WO 01/38061.For example, inhibitors against bonding induced by radiated heat areparticles which reflect radiated heat, for example, metallic inks,silver pigment, or reflective powder, or thermally insulating particles,e.g. ceramic powder or ceramic dispersions. Sintering inhibitors forpolymers include oils, alcohols, or waxes having sufficiently highviscosity to form a coherent film around the pulverulent material toinhibit the sintering-together of the pulverulent materials at thesintering temperature. The process of the invention can also use bondinginhibitors whose inhibition of bonding is achieved by forming mechanicalbarriers between the particles to be melted, or by forming insulatingregions between the particles to be fused.

Oils, alcohols, or waxes may likewise be used as inhibitors for chemicalreactions. For example, the surface of the pulverulent materials ofselective regions of the individual layers may be hydrophobicized, orelse hydrophilicized, using one or more of an oil, alcohol, hydrocarbon,water, or another suitable compound, e.g. a silane. If the entire matrixof built-up layers is finally treated with a crosslinking agent, e.g.with an adhesive, e.g. applied by pouring or spraying of the adhesive,or by immersing the matrix in the adhesive, and if the adhesive hashydrophilic or, respectively, hydrophobic properties, bonding then takesplace only between the pulverulent materials to which no inhibitor hasbeen applied.

Another example of a suitable inhibitor is hydrogen peroxide, which mayreact with a polymer used as pulverulent material to alter the surfacechemistry of the polymer. It is also possible to use brine as inhibitor.Application of brine leads to the formation of crystals on the particlesurface of the pulverulent materials, thereby acting as a chemical, orphysical, separator.

Another suitable inhibitor is water, which may comprise additionalmaterials to improve wetting, e.g. surfactants, of the pulverulentmaterial. The water may inhibit physical bonding of the particles, e.g.because the particles do not melt immediately when exposed to heat inthe regions where the particles have been treated with water, butinstead remain pulverulent due to the cooling action of the vaporizingwater, and therefore do not bond. The use of water can also inhibitchemical reactions. For example, water, or a mixture comprising water,e.g. a water/surfactant mixture, may be used in particular to inhibitanionic polymerization in cases where anionic polymerization is thereaction bonding the particles.

Examples of other inhibitors include dyes which, for example, can serveas filters for radiation of a particular wavelength, and thus caninhibit bonding of the particles.

The pulverulent material used preferably comprises a pulverulentmaterial which has been produced by grinding, precipitation, and/oranionic polymerization, or any combinations of these, specificallyprecipitation of a powder of somewhat too coarse particle size, andsubsequent milling, or precipitation, and subsequent classification.

It is particularly preferred that the pulverulent material has a medianparticle size (d₅₀) of from 10 to 200 μm, particularly preferably from20 to 100 μm, and very particularly preferably from 40 to 70 μm. Anyrange or subrange within 10 to 200 μm may be used, e.g., 10-20, 20-40,20-100, 100-200, 50-150, 10-15 etc. Depending on the intended use, itcan be advantageous to use pulverulent materials which compriseparticularly small and particularly large particles. In order to obtainthree-dimensional articles with maximum resolution and maximum surfacesmoothness, it can be advantageous to use particles whose medianparticle size is from 10 to 45 μm, preferably from 10 to 35 μm, veryparticularly preferably from 20 to 30 μm.

The pulverulent material particularly preferably comprises a polyamide,in particular nylon 12, preferably prepared as described in DE 197 08946, or else DE 44 21 454 (each of which is incorporated herein byreference), and particularly preferably having a melting point and anenthalpy of fusion as given in EP 0 911 142 (incorporated herein byreference), or comprise a copolyamide or copolyester, e.g. as obtainablewith the trademark VESTAMELT® from Degussa AG. The pulverulent materialmay consist of only nylon-12 or may contain other materials.

Fine material of size below 20 μm, in particular below 10 μm, isdifficult to process, because it does not flow freely, and the bulkdensity falls drastically, with the possible result that more cavitiesare produced. To ease handling, it can be advantageous to use particleswhose median particle size is from 60 to 200 μm, preferably from 70 to150 μm, and very particularly preferably from 75 to 100 μm. Thesepulverulent materials may also preferably comprise a polyamide, inparticular nylon 12, or comprise a copolyamide, and/or a copolyester, asdescribed above. If significantly coarser powder is used the layerthickness may conflict with particle size and result in insufficientresolution.

The particle size distribution may be selected as desired for the statedmedian particle sizes of the pulverulent materials. Preference is givento the use of pulverulent materials which have a broad or narrowparticle size distribution, preferably a narrow particle sizedistribution. Mixtures of particles having different particle sizedistribution may be used (e.g., polymodal distribution). Particularlypreferred pulverulent materials for use in the process of the inventionhave a particle size distribution in which, based on the median particlesize, a particle size deviation of more than 50% is present in not morethan 20% of the particles, preferably 15%, and very particularlypreferably not more than 5%. The particle size distribution can beadjusted by conventional classification methods, e.g. pneumaticseparation. Maximum narrowness of particle size distribution in theprocess of the invention gives three-dimensional objects in which thesurface is very uniform and any pores present are very uniform.

At least a part of the pulverulent material used may be amorphous,crystalline, or semicrystalline. Preferred pulverulent material has alinear or branched structure. Particularly preferred pulverulentmaterial has, at least in part, a melting point of from 50 to 350° C.,preferably from 70 to 200° C. The inhibition of sintering procedures viathe use of oils, alcohols, hydrogen peroxide, water, or brine is verypossible in these temperature ranges.

In the process of the invention it is very particularly preferable touse a pulverulent material in which a polyamide, preferably at least oneof nylon 6, nylon 11, and/or nylon 12, or a copolyester, or acopolyamide, is present. Polyamides can produce three-dimensionalmoldings which are particularly dimensionally stable. Particularpreference is given to nylon 12 powder, e.g. as described in EP 0 911142. Preferred copolyamides or copolyesters used are those obtainablewith the trademark VESTAMELT from Degussa AG. Particularly preferredcopolyamides are those having a melting point of from 76 to 159° C.,preferably from 98 to 130° C., and very particularly preferably from 110to 123° C., determined by differential scanning calometry (DSC).Examples of methods of preparing the copolyamides include polymerizationof mixtures of suitable monomers, e.g. those selected from laurolactamand/or caprolactam, as bifunctional component, suberic acid, azeleicacid, dodecanedioic acid, adipic acid, and/or sebacic acid as componentbearing an acid function, and 1,6-hexanediamine, isophoronediamineand/or methylpentamethylenediamine as diamine.

In order to achieve better processibility of the pulverulent materials,it can be advantageous to use a pulverulent material which comprisesadditives. Examples of these additives include flow aids. Thepulverulent material particularly preferably comprises from 0.05 to 5%by weight, with preference from 0.1 to 1% by weight, of additives.Examples of flow aids include fumed silicas, stearates, or other flowaids known from the literature, e.g. tricalcium phosphate, calciumsilicates, Al₂O₃, MgO, MgCO₃, or ZnO. An example of fumed silica issupplied with the trademark AEROSIL® by Degussa AG.

Together with, or instead of, these flow aids, inorganic fillers mayalso be present in a pulverulent material used according to theinvention. Fillers have the advantage that they may substantially retaintheir shape through the treatment during the bonding process, andthereby reduce shrinkage in the three-dimensional object. In addition,the use of fillers permits, for example, alteration of the plasticproperties and physical properties of the objects. For example, thetransparency and color of the object, and/or its magnetic properties,can be adjusted by using pulverulent material which comprises metalpowders. By way of example, glass particles, ceramic particles, or metalparticles may also be present as fillers in the pulverulent material.Typical fillers include granular metals, aluminum powders, steel shot,or glass beads. It is particularly preferable to use pulverulentmaterials which comprise glass beads as fillers. In one preferredembodiment, the pulverulent material of the invention comprises from 1to 70% by weight of fillers, preferably from 5 to 50% by weight, andvery particularly preferably from 10 to 40% by weight. All ranges andsubranges including for example 1-2,2-4, 5-10, 10-20, 20-40, 25-50 etc.are included.

Together with, or instead of, inorganic flow aids or fillers, inorganicor organic pigments may also be present in the pulverulent material.These pigments may be not only color pigments which determine theperceived color of the three-dimensional body to be generated, but mayalso be pigments that affect other physical properties of thethree-dimensional articles, examples include magnetic pigments, and/orconductivity pigments, e.g. conductivity-modified titanium dioxide ortin oxide, which alter the magnetic properties and, respectively, theconductivity of the article. The pulverulent material particularlypreferably comprises inorganic or organic color pigments selected fromchalk, ochre, umber, green earth, burnt sienna, graphite, titanium white(titanium dioxide), white lead, zinc white, lithopone, antimony white,carbon black, iron oxide black, manganese black, cobalt black, antimonyblack, lead chromate, minium, zinc yellow, zinc green, cadmium red,cobalt blue, Prussian blue, ultramarine, manganese violet, cadmiumyellow, Schweinfurter green, molybdate orange, molybdate red, chromeorange, chrome red, iron oxide red, chromium oxide green, strontiumyellow, metallic-effect pigments, pearlescent pigments, luminescentpigments using fluorescent and/or phosphorescent pigments, umber,gamboge, animal charcoal, Cassel brown, indigo, chlorophyll, azo dyes,indigoids, dioxazine pigments, quinacridone pigments, phthalocyaninepigments, isoindolinone pigments, perylene pigments, perinone pigments,metal complex pigments, alkali blue pigments, and dicetopyrrolopyrrole.Further information concerning pigments which may be used may be foundin, for example, Römpp Lexikon Chemie [Römpp ChemicalEncyclopedia]—Version 2.0, Stuttgart/New York: Georg Thieme Verlag 1999,and also in the references given in that publication. The particle sizesof the pigments used may be those described for the pulverulentmaterial. However, the pigments frequently have particle sizessignificantly smaller than the median particle sizes of the polymersused. The pigments may, for example, be applied in a manner similar tothat for the bonding inhibitors such as through nozzles used in printingheads, or may be present in the polymer particles. The pulverulentmaterial of the invention particularly preferably comprises polymerparticles which comprise one or more of the pigmentsmentioned—preferably with the exception of white pigments alone. Theproportion of the pigments in the pulverulent material is preferablyfrom 0.01 to 25% by weight, preferably from 0.1 to 10% by weight, andparticularly preferably from 1 to 3% by weight.

In the process of the invention, the moldings produced therefrom mayhave one or more functionalized layers. By way of example,functionalization, e.g. the provision of conductive properties to theentire molding, or else only to certain regions, may take place byapplying appropriate pigments or substances to the layer or pulverulentmaterial, using a method similar to that for the inhibitor.

One embodiment of the process of the invention, use includes of bondinginhibitors whose action is only temporary. These bonding inhibitors maybe frames, plates, sheets, or glass materials of various shape, wherethese may comprise two or more parts, and where, after application ofthe powder, bonding inhibitors protectively cover regions of the powderlayer in the manner of a frame. By using a large number of differentshapes, or by using flexible shapes which can be adapted by computercontrol to the area to be protectively covered, it is possible toprovide protective covering for almost any conceivable cross-sectionalarea. The pulverulent material in the area not protectively covered isbonded, together and to adjacent underlying layers, by exposure toradiation, in particular radiated heat, or by spraying with a chemical.The temporary bonding inhibitors are then removed, and a fresh layer ofpulverulent material is applied. This embodiment of the process of theinvention also gives a three-dimensional article by repeating the stepsof the process as required by the number of cross-sectional areas. Thepulverulent materials used may be the abovementioned materials.

Moldings which can be produced by the process of the invention can haveany desired three-dimensional shape which can be formed by layers. Themolding particularly preferably comprises a nylon 12, a copolyamide, ora copolyester. Moldings produced using the process of the inventionpreferably comprise at least one filler selected from glass beads oraluminum powder. Moldings which can be produced by means of the processof the invention are in particular those whose color is neither whitenor transparent (nor transparent with a milky or yellowish effect).Moldings with these colors cannot be produced using conventionallaser-sintering processes, because the color pigments impair the supplyof energy by the laser. The moldings produced according to the inventionmay also have functionalized layers. Besides functionalization throughpigments, there may also be compounds with particular functionalproperties present in one or more of the layers, or in the entiremolding. An example of functionalization may consist in provision ofelectrically conducting properties to the entire molding, to one or morelayers of the molding, or else only to parts of one or more layers ofthe molding. This functionalization may be achieved through conductivepigments, e.g. metal powders, or through the use of conductive polymers,e.g. polyaniline. Moldings which have conductor tracts can be obtainedin this way, and these may be present either on the surface or elsewithin the molding.

The present invention also provides the pulverulent material asdescribed above, suitable for use in the process of the invention, andin which, in particular, the median particle size is from 10 to 200 μm,and in which at least one polymer or copolymer selected from polyvinylchloride, polyester, polyacetal, polypropylene, polyethylene,polystyrene, polycarbonate, PMMA, PMMI, ionomer, polyamides,copolyester, copolyamides, terpolymers, or ABS, or a mixture of these,is present. The powder particularly preferably comprises nylon 12, acopolyamide, or a copolyester, or a mixture of these. The powderparticularly preferably comprises polymer particles which have beencolored, their color being other than white.

EXAMPLES

Triangular objects with edge length 50×50 mm were produced by means ofthe process of the invention for the selected inhibition of bonding. Forthis, a square metal frame with internal dimensions of 50 mm andexternal dimensions of 100 mm, with a thickness of 1 mm, was placed on acontinuous metal plate. The resultant aperture was then filled withpowder and another metal plate was used for smoothing. One half of therectangle was then protectively covered, using a flexible metal plate.The remaining powder surface was then uniformly wetted, byspray-application, using an air-brush gun, with water which had beentreated with 10% by weight of a washing composition (Pril, Henkel).After removal of the protective covering, the entire powder layer washeated for 2 and, respectively, 5 seconds at a distance of 2 cm from aradiant heater from the company AKO, having a power rating of 1000watts. This gave a powder layer including, as component, a triangularstructure comprising sintered powder. The powder which was presentaround the component and which was treated with the water comprisingwashing composition during the production process remained in powderform. The component could be removed without difficulty from the powderlayer. Table 1 below lists the powders tested, and the results of theexperiments. TABLE 1 Melting point Pulverulent (DSC) material Trade namein ° C. Result Copolyamide Vestamelt X1310 110 No curl, goodsinterability, sharp edges PA12 EOSINT PA 186 Good sinterability, slightcurl 2200 PA612 Vestamid D16 216 Sinterable Copolyester Vestamelt 4481107 Good sinterability Copolyamide Vestamelt 840 113 Very goodsinterability, the inhibitor-covered parts also sintered when using 5seconds of irradiation; when using 5 seconds and a distance of 10 cm,edges were not sharp PE Vestolen A6016 Good sinterability, curl EPVCVestolit P1403 K Sinterable, discoloration MPVC Vestolit P2004Sinterable, KF discoloration

The abbreviations MPVC and EPVC indicate the PVC production method: MPVCrepresents mass-polymerized polyvinyl chloride, and EPVC representsemulsion-polymerized polyvinyl chloride. PE represents polyethylene.

The products with the Vestamelt and Vestamid can be purchased fromDegussa AG. The product EOSINT PA 2200 can be purchased from EOS GmbHElectro Optical Systems. The product Vestolen is obtainable via SabicEPC, and the products with the name Vestolit are obtainable via VestolitGmbH & Co KG. The abovementioned product names are registered trademarksof the respective stated companies, with the exception of the nameVestolen, which is registered as a trademark of DSM Polyolefin GmbH,Gelsenkirchen, Germany.

German applications 10244047.6 and 1031146.7 filed on Sep. 21, 2002 andMar. 15, 2003, respectively, are each incorporated herein by referencein their entireties.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A process for producing a three-dimensional object, comprising: a)providing a layer of a pulverulent material, b) applying one or morebonding inhibitors to one or more regions of the layer wherein theregions to which the bonding inhibitor is applied are the cross sectionregions of the three-dimensional object, and wherein no bondinginhibitor is applied to regions which are not the cross section regionsof the three-dimensional object, c) repeating a) and b) until all of thecross-section regions of the three-dimensional object are a matrix ofinhibitor-applied pulverulent layer regions, wherein the outerboundaries of the three-dimensional object are the interface betweeninhibitor-applied pulverulent material and pulverulent material withoutapplied inhibitor, and d) treating the layers at least once to bond thepulverulent material which does not have applied inhibitor, wherein thepulverulent material has a median particle size of from 10 to 200 μm andcomprises at least one selected from the group consisting of apolyester, a polyvinyl chloride, a polyacetal, a polypropylene, apolyethylene, a polystyrene, a polycarbonate, PMMA, PMMI, an ionomer, apolyamide, a copolyester, a copolyamide, a terpolymer, ABS and a mixturethereof.
 2. The process as claimed in claim 1, wherein d) is carried outafter b).
 3. The process as claimed in claim 1, wherein d) is carriedout after c).
 4. The process as claimed in claim 1, wherein thepulverulent material is obtained by grinding, precipitation, anionicpolymerization, or a combination thereof, with optional subsequentfractionation thereof.
 5. The process as claimed in claim 1, wherein thepulverulent material comprises at least one of nylon-6, nylon-11 ornylon-12.
 6. The process as claimed in claim 1, wherein the pulverulentmaterial is amorphous or semicrystalline.
 7. The process as claimed inclaim 1, wherein the pulverulent material has a linear or branchedstructure.
 8. The process as claimed in claim 1, wherein at least aportion of the pulverulent material has a melting point of from 50 to350° C.
 9. The process as claimed in claim 1, wherein at least a portionof the pulverulent material has a melting point of from 70 to 200° C.10. The process as claimed in claim 1, wherein the pulverulent materialhas a median particle size of from 20 to 100 μm.
 11. The process asclaimed in claim 1, wherein the pulverulent material comprises from 0.05to 5% by weight of one or more flow aids.
 12. The process as claimed inclaim 1, wherein the pulverulent material comprises one or moreinorganic fillers.
 13. The process as claimed in claim 12, wherein thefillers comprise glass beads.
 14. The process as claimed in claim 1,wherein the wherein pulverulent material comprises one or more inorganicpigments, organic pigments, or both.
 15. The process as claimed in claim1, wherein the bonding inhibitor comprises a material with wettingproperties.
 16. The process as claimed in claim 1, wherein the bondinginhibitor comprises at least one liquid selected from the groupconsisting of water, an oil, and an alcohol.
 17. The process as claimedin claim 1, wherein the bonding inhibitor temporarily inhibits bonding.18. The process as claimed in claim 1, wherein the bonding inhibitorcomprises water and at least one surfactant.
 19. The process as claimedin claim 1, further comprising inhibiting bonding of theinhibitor-applied pulverulent layers by vaporization and cooling. 20.The process as claimed in claim 1, further comprising inhibiting bondingof the inhibitor-applied pulverulent layers by forming one or moremechanical barriers between the particles of pulverulent material of theinhibitor-applied pulverulent layers.
 21. The process as claimed inclaim 1, further comprising inhibiting bonding of the inhibitor-appliedpulverulent layers by forming one or more thermally insulating regionsbetween the particles of pulverulent material of the inhibitor-appliedpulverulent layers. 22-26. (canceled)